Process of fireproofing



Patented June 15, 1942 PROCESS OF FIREPDOOFING Martin Leather-man,Hyattsvllle, Md.

No Drawin 8. Original appli cation November 20,

1935, Serial No. 50,763, now Patent No. 2,167,278, dated July 25, 1939.Divided and this applicaon July 5, 1939, Serial No. 282,950

Claims. (CL 117-137) (Granted under the act of March 3, 1883, as amendedApril 30, 1928; 370 0. G. 757) This application is made under the act ofMarch 3, 1883, as amended by the act of April 30; 1923, and theinvention herein described and claimed, if patented, may be manufacturedand used by or for the Government of the United States of America forgovernmental purposes without the payment to me of any royalty thereon.

This application is a division of my pending application for patent,Serial No. 50,763, filed November 20, 1935. This application resulted inthe issuance of United States Patent No. 2,167,278.

This invention relates to fireprooflng compositions for cellulosicmaterials and is not to be confused with the fire-resistant coatingsabounding in the art which merely burn with difilculty and do not impartfireproof qualities to the materials in or on which they may beincorporated.

The impregnation of cotton fabrics with tin oxide for the purpose ofimparting flame-resistance thereto is well known. This process involvesfirst impregnating the fabric with a stannate solution, then drying,followed by precipitating and setting the tin oxide by saturating thefabric with a solution of ammonium, sulfate. This is the proceduredeveloped by Perkin (U. S. Patent No. 856,906). By this process thecellulosic material develops a complete inability to propagate flame butit will nevertheless burn without flame, that is by a continuous processof incandescent glowing.

A later discovery improves the Perkin process by impregnating the fabricwith a chlorinated resin which prevents the flameless combustion.

-However, the fabric deteriorates rapidly when exposed to sunlight,whether it contains the tin oxide only or the tin oxide plus thechlorinated resin. Still more recent discoveries involve the use ofmetallic salt solutions for precipitating and setting the tin oxide inthe fabric. 'By this process the fabric can be given a limited range ofcolor which has been found to lessen the deterioration by sunlight. Thisprocess also involves the final addition of a chlorinated resin to theoxide-impregnated fabric.

All of these prior processes require specialized machinery in theirapplication. They also involve a series of steps which increase the costof the finished product and lessen the field of usefulness.

It appears that the fiameproofing property is a function of the surfacecharacteristics of the oxide. Tin oxide is highly colloidal asprecipitated by the Perkin process and therefore has an enormous surfacearea. If the tin oxide is precipitated in mass, washed somewhat anddried, the colloidal particles coalesce and the oxide loses most of itsflameproofing power. A

considerable number of metallic oxides are capa-' ble of flameproofingcellulosic materials provided their physical state is suitable. In theprior art tin oxide was the only metal oxide thatlcould be,

'held so tightly because of its gel-like colloidal nature that it wouldnot dust off of the cellulose fibers. There seemed to be aphysico-chemical bond existing between the oxide and thecellulose andthis was assumed to have something to do with the flameproofingcapacity.

However, I have now made a very remarkable discovery. I have found that,provided the proper physical state is retained, the fiameproofing oxidesreferred to hereinafter do not require to be in immediate contact withthe cellulose material in order to impart fiameproofness. That is, I canbind the oxides to the cellulosic material in a matrix of chlorinatedresin and the cellulose will still be flreproof. The oxide particles areactually suspended in the resin matrix which .in turn adheres to thecellulose fibers. This procedure leads to very unexpected results. Aslong as the oxides are directly in contact with the cellulosic materialthe tendency to flameless combustion reappears as soon as thesuperimposed chlorinated resin is destroyed by combustion temperatures,that is; glowing is quite evident in charred areas. However, when theoxide is suspended in the resin matrix the tendency to glow in charredportions is visibly lessened.

When'the oxide particles are dispersed in the resin matrix, thepigmenting power of a given fireprooflng oxide mixture appears to belessened and, as a result, deterioration of the fabric upon exposure tosunlight is accelerated. This is largely due to decomposition of thechlorinated resin accompanied by liberation of hydrogen chloride. I havefound that by incorporating an additional quantity of an inert pigmentintomy composition,- I can remedy this condition. All pigments are ofvalue but I find those which contain yellow as one color component areespecially valuable. Ihave further found that those pigments in whichlead is present tend to accelerate glowing in charred portions but thisis unduly objectionable.

The very great advantage accruing from my not discovery is that, for thefirst time, it becomes.

possible to prepare a truly weather-resistant fireproofing compositionwhich can 'be applied to wood, cotton and other cellulose-base materialsby the simple process of mixing, dipping, painting or spraying. Forexample, fabric treated with my composition by simply dipping it intothe composition and then drying, is completely and permanentlyfireproof.

for the first time to prepare a paint-like compo- It now becomespossible rately and mix the separate aqueous suspensions;

sition which can be used in the home or else-- where for finishing orrefinishing cotton fabrics. My composition .has many ramifications andapplications.

In its most valuable aspect my, composition is comprised of threecomponents, the oxide component, the resin component and a volatilesolvent vehicle.

The final .character of the oxides in my composition is all important indetermining fireproofing capacity. I may use one or a combination of theoxides of tin, lead, aluminum, titanium, germanium, zirconium, vanadium,chromium, manganese, iron, cobalt, nickel, copper, cadmium and zinc, theterm oxide to include hydrated oxides. In the case of some of the oxidesmentioned the oxide will have little direct fireproofing capacity andwill act chiefly to increase or preserve the fireproofing action ofanother oxide with which it is, mixed. Iron oxide, for example, has veryslight fireproofing capacity alone but markedly increases thefireproofing action of tin oxide.

For reasons of expediency or economy I may prefer to use tin or leadoxide combined with one or more of the other oxides mentioned. In thatcase I may proceed as follows: A solution of a stannate, stannite,plumbate or plumbite is mixed with a solution of a salt of one or moreof the metals mentioned above. I may use the solutions in chemicallyequivalent amounts or I may use-an excess of .the metallic salts andprecipitate the excess with an added base as a final step. By thisprocedure the alkaline stannate, stannite, plumbate or plumbite reactswith the acidic metal salt with a resultant mutual precipitation of tinor lead oxide with one or more other metal oxides.

' As a result, the gel-like colloidal tin or lead oxides are intimatelyintermingled with one or more other oxides with crystalline tendencies,and the precipitated mixture can be filtered, washed and dried and willstill be easily reduced to an impalpable powder. A mutual interferenceis set up in the mixture. On the one hand, the hydrated tin or leadoxide particles do not coalesce and on the other, the particles of thesecond oxide do not agglomerate to form a crystal structure.

I may utilize any metal which forms com or the aqueous suspensions ofthe precipitated oxides might be atomized into an evacuated dryingchamber. Besides precipitation methods I may use other means ofpreparing the metallic oxides in effective form,-such, for example, asreduction in preparing manganese dioxide.from permanganates; alternatereduction and oxidation in the, case of copper oxide; in short anymethod which yields a satisfactory final product. For these reasons I donot restrict myself to any manner of preparation or combination of theoxides in my composition but limit myself only to the fireproofingproperties present in the prepared oxide or oxide'mixture.

The resin component may be any one or more of a wide range ofchlorinated materials, depending upon the use to which the compositionis to be put. For use in coating or impregnating textiles a verydesirable resin is made by chlorinating a mixture of parafiin wax andpetroleum oils. A' wide variety of mineral or petroleum oils may beutilized in the mixture. The chemical complexity of such oils is adesirable feature since it leads to greater thermal instability in thefinished chlorinated resinous product; Such a chlorinated resinousmixture evolves hydrogen chloride freely when thermally decomposed andhydrogen chloride is an effective combustion preventing gas. By varyingthe melting point and by using various proportions of paraflin wax inthe wax-oil mixture and also by varying the viscosity and I type of theoils used, any desired physical state can be obtained in the finishedchlorinated product. In general, the chlorine content may approximate 60percent by weight of the finished product but I do not restrict myselfon this point since considerable latitude is possible.

In treating cellulose fibers with my. paint composition, the nature ofthe chlorinated resin is extremely important. I am notaware of-all thefactors involved but it appears that the property known as wetting powerplays a large part. This property is no doubt associated with solutionviscosity which in turn is probably related to the size of the resinmolecule. .At any rate, I have found that compositions prepared withvinyl resins and with chlorinated rubber are of much less value infireproofing cotton fabrics. There are many materials which can bechlorinated to yield resins which, in organic solution, possess thenecessary wetting power. Also, the natural oils, fats and waxes, andlong chain alcohols and acids will produce suitable resins uponchlorination.

Another resinous material which is very effective in my composition forpurposes other than textile fireproofing is represented by thechlorinated vinyl resins. These resins also evolve hydrogen chloridewhen heated, and they are usual- 1y solid bodies. A compositioncomprising the fireproofing metallic oxide component and the chlorinatedvinyl resin can be used for impregnating textiles but the fireproofqualities imparted are much less. However, the vlscositles of a volatilesolvent solution-suspension of the vinyl resin-oxide composition arehigher than the viscoslties obtainable with a correspondingconcentration of the chlorinated wax-oil resin described above, andthorough impregnation of textiles therefore is more diflicult; One useto which the chlorinated vinyl resin-oxide composition mayadvantageously be put is in binding together shredded corn stalks,sawdust, straw and thelike in preparation of structural and acousticalblocks, panels and the like. Such products will be rendered highly fireresistant by my composition.' The vinyl resins are capable of impartingconsiderable structural strength to such products. Another product whichcan be utilized toadvantage in my composition is chlorinated rubber.Chlorinated rubber resins can be made highly water-repellent and whenfireproofing oxides are incorporated into these resins an excellentcoating composition for wood shingles and the like is obtained. It is tobe understood,

however, that the uses indicated by me for the compositions comprised ofthe various materials does not preclude the possibility of using thevarious compositions interchangeably. Then too I may combine the variousresinous materials in any manner I find advantageous.

In addition to the foregoing materials I may utilize chlorinatednaphthalene derivatives 'and the so-called chlorinated diphenylderivatives in my composition. Also a'very' satisfactory chlorinatedproduct can be obtained by chlorinating and polymerizing paracymene as atypical representative of the aryl-alkyl compounds. These mixed types ofcompounds yield very effective fireproofing resins when chlorinated. I

This will indicate the wide variety of chlorinated resinous materialswhich I can employin my compositions: It is understood, of course, thatother halogens may be the equivalent of chlorine in preparing the resincomponent of my compositions.

As to the relative proportions of oxide component and chlorinated resincomponent, consid- 6 on the material being treated, but also the lowermerely to regulate the proportions of fireproofing composition relativeto the material being fireproofed. Obviously the more solvent used theless oxide-resin composition will remain in or will be the viscosity ofthe suspension solution and the more thoroughly the oxide-resin mixturewill be impregnated into a fibrous base. For fireproofing textiles theproportion of solvent is 10 such as to deposit, upon evaporation,oxide-resin mixture in amount equal to from 25 to 50 percent of thetreated fabric by weight but I do not restrict my proportions rigidlywithin these limits. I may find it expedient to emulsify the oxide-resinmixture in water and thereby eliminate the solvent component entirely.

In the case of a thermally plastic chlorinated resinwhere theoxide-resin composition is being used to bind sawdust or fibrousmaterials into a rigidshape I may dispense with all volatile solvent. Asvolatile solvent I may employ any solvent which is compatible with thegiven resin which I may require, and which will be lost by evaporationwithin the temperature range 5 through which the resin is stable.

In addition to theoxide component, the resin component and the volatilesolvent I may include in my composition plasticising and siccatve agentsto modify the physical properties of my compositions. By plasticizingagent I denote any material which softens the chlorinated resin and by asiccative I indicate any material which lessens tackiness. A widevariety of plasticizers are available. Among those which I may use aretricresyl phosphate, triphenyl phosphate, dibutyl phthalate, tung oil,beeswax and chlorinated dihenyl. I may also include in my compositionagents which have mildew-proofing properties, other than such compoundsas copper oxide which are mentioned herein. Other compounds of coppermay be used such as copper chromate or I may use organic fungicideswhich are insoluble in water.

Finally I may include any desired mineral or 5 oxide pigment in mycomposition. Such pigerable latitude is allowable. For use in impreg- Inating textiles I have found that-proportions of the order of one partof oxide component to two parts of resin component by weight effectivelyfireproof-cellulosic materials when properly incorporated therein.Obviously within the spirit of my invention these proportions may bevaried widely, and, again, I restrict myself only by the resultsobtained. In general, the more effective the fiameproofing action of theresin employed the less the proportion of 'oxide required. In the casewhere the resin component is low in fiameproofing action 'the proportionof oxide will have to be increased. One measure of the effectiveness ofa given chlorinated resin is the volume of hydrogen chloride evolvedduring thermal decomposition as compared to any other resin.

Before considering the third component of my composition, I wish todefine the term resin as I have used it. By resin I indicate thoseliquid, semi-solid or solid bodies, obtained by chlorination, which areindefinite in physical characteristics, such as melting point, in thatthey change from the liquid to the solid state and vice versa through anappreciable temperature range. To an even greater extent these bodiesare characterized by indefiniteness of chemical composition.

The volatile solvent vehicle in my composition plays no part in thefireproofing action and serves 75 merits will usually have nofireproofing properties. An oxide used for pigmenting purposes may havebeen prepared in such a manner as to have no fiameproofing properties,even though such properties might be inherently present. For example,

sintered stanic oxide posseses no fiameprooflng,

properties, whereas stannic oxide prepared in the manner specifiedherein does possess excellent fiameproofing properties. By propercombinations of pigments and fireproofing. oxides in my composition I amable to obtain any color desired.

In preparing my composition in paint form, which will be that used intreating textiles, the resin will be dissolved in a compatible volatilesolvent and the oxide component will be ground with the solution by useof the usual paint grinding equipment such as ball mills, burr mills,colloid mills, etc. I may add both the fireproofing oxide and thepigment at the commencement of grinding or I may addthe pigment afterthe grinding is nearly completed. It will be understood that thefireproofing oxides must be as fine as possible to permit the resinsolution to carry the oxide particles the more thoroughly through outthe fabric. The pigment, on the other hand, exerts its maximumprotective function if it is chiefly on the outer surface of the fabricthreads and, therefore, it is not essential that the pigment particlesbe so highly dispersed. However, this tin, lead, aluminum, titanium,germanium, zirconium, vanadium, chromium, manganese, iron, cobalt,nickel, copper cadmium, and zinc, in an organic solution of achlorinated resin, the metallic element of one of said oxides beingchosen:

from the group consisting of tin and lead followed by drying saidcoating.

2. The process of flreprooflng a cellulosic-base material comprisingcoating the material with a suspension of a plurality of metallic oxidesselected from the group consisting of oxides of tin, lead, aluminum,titanium, germanium, zirconium, vanadium, chromium, manganese, iron,cobalt, nickel, copper cadmium, and zinc, in an organic solution ofclilorinated paramn wax and chlorinated petroleunr oil, the metallicelement of one of said oxides being chosen from the group consisting oftin and lead followed by drying said coating.

3. The process of fireproofing a cellulosic-base material comprisingcoating the material with a suspension of a plurality of metallic oxidesselected from the group consisting of oxides of tin, lead, aluminum,titanium, germanium, zirconium,vanadium, chromium, manganese, iron,cobalt, nickel, copper, cadmium, and zinc, in an organic solution of achlorinated resin, the metallic element of one of said oxides being tin.

4. The process of fireprooiing a cellulosic-base material comprisingcoating the material with a suspension of a plurality of metallic oxidesselected from the group consisting of oxides of tin, lead, aluminum,titanium, germanium, zirconium,. vanadium, chromium, manganese, iron,cobalt, nickel, coppencadmium, and zinc, in an organic solution of achlorinated resin, the metallic element of one of said oxides beinglead.

5. The process of fireproofing a cellulosic-base material comprisingcoating the material with a suspension of oxides of tin and iron in anorganic solution of a chlorinated resin followed by drying said coating.1

6. The process of fireproofing a cellulosic-base material comprisingcoating the material with a suspension of oxides of tin and iron in anorganic solution of chlorinated resin followed by drying said coating,said suspension being produced by combining in water solution sodiumstannate and iron sulfate, separating and recovering the metallic oxidesformed, washing and drying the recovered oxides and suspending the driedoxides in an organic solution of a chlorinated resin.

7. The process of flreproofing a cellulosic-base material comprisingcoating the material with a suspension of oxides of tin and iron in anorganic solutionof chlorinated resin followed by; drying said coating,said suspension being produced by combining in water solution awater-soluble stannate'and a water-soluble iron salt of a strong mineralacid, separating andv recovering the metallic oxides formed, washing anddrying the recovered oxides and suspending them in an organic solution.

8. The process of flreproofing a cellulosic-base material comprisingcoating the material with a suspension of oxides of tin, iron andchromium in an organic solution of a chlorinated. resin followed bydrying said coating.

9. The process of fireproofing a cellulosic-base material comprisingcoating the material with a suspension of oxides, of tin, iron andchromium in an organic solution of a chlorinated resin followed bydrying said coating, said suspension being produced by combining inwater solution a water-soluble stannate, a water-soluble firon of astrong mineral acid and a water-soluble chromium salt of a strongmineral acid, separating and recovering the metallic oxides formed,washing and drying the recovered oxides and suspending them in theorganic solution.

10. The process of fireproofing a cellulosic-base material comprisingcoating the materialwith a suspension of oxides'of tin and cadmium in anorganic solution of a chlorinated resin followed by drying said coating.

- MARTIN LEATHERMAN.

